In the image forming apparatus employing electrophotographic method, there is a problem of griming an image that toner from a developing device which wafts, grimes and accumulates inside the apparatus, spills on a transfer sheet and grimes an image. In particular, in case of an image forming apparatus having a long print durability to continue printing for a long time without stopping the apparatus, it is a big problem.
To cope with the above problem, in Patent Document 1: Unexamined Japanese Patent Application Publication No. H08-220882, there is suggested a method using so called a developer suction to suction the wafting toner at a periphery of the developing device from a suction opening of a ventilation duct. In this method, the wafting toner is suctioned and collected by a filter so to prevent image forming processing members (constituent element) and transfer members (sheet) from griming.
However, in the method using developer suction described in the Patent Document 1, there is a problem that the filter has to be replaced frequently since the filter collects the wafting toner.
Then, in Patent document 2: Unexamined Japanese Patent Application Publication No. 2007-86436, there is suggested another method to collect the wafting toner by disposing a separate collecting member from suctioning the wafting toner until collecting the wafting toner by the filter. In the method of the Patent Document 2, a baffle member is disposed on the way in the ventilation duct before the suctioned wafting toner reaches to the filter so that a part of the wafting toner is collected by the baffle member. In the Patent Document 3: Unexamined Japanese Patent Application Publication No. 2001-255797, there is suggested a cyclone separation method to collect the toner on the way in the ventilation duct before collecting the toner by the filter. As above, by collecting the toner on the way in the ventilation duct, an amount of the toner reaches to the filter is reduced and replacing of the filter is decreases in the frequency.    Patent Document 1: Unexamined Japanese Patent Application Publication No. H08-220882    Patent Document 2: Unexamined Japanese Patent Application Publication No. 2007-86436    Patent Document 3: Unexamined Japanese Patent Application Publication No. 2001-255797
In the methods of the Patent Documents 2 and 3, the toner collected on the way in the ventilation duct has to be recovered. In the Patent Document 2, though the buffer member is replaced as a collecting box, replacing of the collecting box increases in the frequency. In the Patent Document 3, since an exclusive toner recovery container is disposed, the size of the apparatus increases and the recovery container has to be stored as a maintenance parts which results in cost increase.